This study's primary objective is to assess the safety, tolerability, and antiviral activity of ABT-378/ritonavir in combination with two nucleoside reverse transcriptase inhibitors (at least one of which the patient has not received before) and nevirapine in protease inhibitor experienced HIV-infected patients. The secondary objective is to determine the steady-state pharmacokinetic profile of ABT-378/ritonavir and nevirapine in protease inhibitor experienced HIV-infected patients.